Precipitation treatment of alloys, such as aluminum alloys, is well known in the prior art as identified for aluminum alloy 6061 and aluminum alloy 2024 in Kirk-Othmer Encyclopedia of Chemical Technology. Third Edition Volume 2, 1978, page 177-178. The recited aging treatment is "natural aging", due to its processing at essentially ambient temperatures.
As set forth in Principles of Materials. Science and Engineering. W. Smith, McGraw-Hill, New York, 1986. Chapter 9, page 478-479and 490-491, precipitation strengthening or hardening is known to create a heat treated alloy of dense and fine dispersion of precipitated particles in the matrix of deformable metal. The precipitate particles act as obstacles to dislocation movement and thereby strengthen the heat treated alloy. The treatment is known to include a solution heat treatment to create a uniform solid solution structure. The alloy is then quenched, typically with cooling water, to room temperature to produce a super saturated solid solution. Finally, the alloy is aged either by "natural aging" at ambient temperatures or "artificial aging" at elevated temperatures to form finely dispersed precipitates. These fine precipitates in the alloy impede dislocation movement during deformation by forcing the dislocations to either cut through the precipitate particle or go around them, thereby strengthening the alloy. Alloys susceptible to such treatment include the wrought and forged aluminum alloys designated: 2XXX, 6XXX, and 7XXX and the cast aluminum alloys designated: 2XX, 3XX and 7XX. The 2XXX alloy is aluminum principally alloyed with copper. The 6XXX alloy aluminum is principally alloyed with magnesium and silicon. The 7XXX aluminum alloy is principally alloyed with zinc, magnesium and copper. The 2XX cast aluminum alloy is principally alloyed with copper. The 3XX cast aluminum alloy is principally alloyed with silicon and copper or silicon and magnesium or silicon and magnesium and copper. The 7XX cast aluminum alloy is principally alloyed with zinc, magnesium and copper.
These designations for cast and wrought aluminum and aluminum alloys are well known in the art, such as in Metals Handbook, desktop edition by Howard E. Boyer and Timothy L. Gall, American Society for Metals. Metals Park, OH, Chapter on Aluminum, 6-8 through 6-10 and 6-23.
The designation to 2XXX, 6XXX and 7XXX for wrought and forged alloys and 2XX. 3XX and 7XX for cast alloys is further demonstrated to be a well recognized nomenclature in the prior art by reference to Structure and Properties of Engineering Materials, Brick, Perse and Gordon, McGraw-Hill, 1977, Chapter on Aluminum Alloys, Page 187 and 188 and Pages 191 through 193.
Various fluorocarbons are known in the prior art, such as those recited in U.S. Pat. No. 2,459,780 which describes the heat transfer capabilities of fully fluorinated and fully saturated carbon compounds.
These compounds are additionally disclosed in Tetrahedron, 1963 Volume 19, page 1893 and 1899. and in an article entitled "Polycyclic Fluoro Aromatic Compounds III", Harrison, et al.
The use of heating solder for vapor phase soldering using fluorocarbons has been disclosed in U.K. patent application GP2110204A.
Additional fluorocarbons useful for vapor phase soldering are identified in U.K patent application GP2194231A.
The use of perfluorotetradecahydrophenanthrene has been set forth in U.S. patent 4,549,686.
The artificial aging of alloys is currently performed in two types of furnaces, either a salt bath or an air chamber furnace. Both of these furnaces have inherent problems. Air furnaces suffer from poor temperature uniformity, while salt bath furnaces create environmental, waste disposal and safety concerns. There exists a need to provide a process for the artificial aging of alloy parts that will overcome these present problems.
More particularly, temperature variations, particularly with air chamber furnaces can lead to overage parts that are either reheat treated or scrapped due to unacceptable physical properties. Military specification MIL-I-6088F and Pratt & Whitney specification PWA-11AK specify a maximum temperature deviation of 10.degree. F. from set point, which can be difficult to achieve with this type of furnace.
Additionally, parts treated in salt baths can entrap sodium nitrate salts from the aging heat treatment. The entrapped salt can react with quench water to form compounds that attack the alloys being treated. Salt entrapment after the alloy parts are removed from the salt bath requires another processing step for the entrapped salts removal, thereby decreasing productivity and increasing production cost.
There are ever growing environmental concerns about the salts used in salt bath furnaces. The disposal of used salts is becoming increasingly more difficult and expensive. Salt bath furnaces are a safety and environmental problem in the work place when water comes into contact with the molten salt which can cause explosions. Finally, the vapors given off from salt baths are often toxic.
In order to overcome the disadvantages in the artificial aging of alloys at elevated temperatures, it is necessary to provide a consistently uniform heat source that is inert to the treated alloy, economical in supply and not subject to degradation, particularly to toxic byproducts, and not susceptible to environmentally difficult disposal. The present invention achieves all of these goals by overcoming the disadvantages of the prior art recited above. The present invention will be set forth below in detail.